<template>
  <div class="pagination">
    <button @click="changePageNo(pageNo - 1)" :disabled="pageNo===1">上一页</button>
    <button v-show="startAndEnd.start>1" @click="changePageNo(1)">1</button>
    <span v-show="startAndEnd.start>2">...</span>
    <button v-for="(_,index) in (startAndEnd.end - startAndEnd.start + 1)" :key="_" :class="{active: pageNo===startAndEnd.start+index}" 
    @click="changePageNo(startAndEnd.start+index)">{{startAndEnd.start+index}}</button>
    <button v-show="startAndEnd.end<totalPage-1">···</button>
    <button v-show="startAndEnd.end<totalPage" @click="changePageNo(totalPage)"> {{totalPage}}</button>
    <button @click="changePageNo(pageNo + 1)" :disabled="pageNo===totalPage">下一页</button>

    <span>共 {{total}} 条</span>
  </div>
</template>

<script>
export default {
    name: "Pagination",
    props: ['total', 'pageNo', 'continues', 'pageSize', 'changePageNo'],

 

    // 计算起始结束页
    computed: {
        totalPage() {
            const {total,  pageSize} = this
            return Math.ceil(total/pageSize)
        },
        startAndEnd() {
                const {continues,pageNo ,totalPage} = this
                let start, end
                if(continues >totalPage ) {
                    start = 1
                    end = totalPage
                }else {
                    start = pageNo - (continues-1)/2
                    end = pageNo + (continues -1)/2
                    
                    if(start < 1) {
                        start = 1
                        end = continues
                    }
                    if(end > totalPage) {
                        start = totalPage - continues + 1
                        end = totalPage
                    }
                }
                return {start, end}
            }
    }
    



};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #C81623;
      color: #fff;
    }
  }
  span{
    display: inline-block;
    line-height: 28px;
    font-size: 14px;
    color:gray;
    vertical-align: middle;
  }
}
</style>